This invention generally relates to a system for detecting electrical activity or signals within a patient's heart and particularly for determining the source of signals causing arrhythmia from within a blood vessel of the patient's heart.
Prior methods for treating a patient's arrhythmia include the use of antiarrhythmic drugs such as sodium and calcium channel blockers or drugs which reduce the Beta-adrenergic activity. Other prior methods include surgically sectioning the origin of the signals causing the arrhythmia or the conducting pathway for such signals. More frequently, however, to terminate the arrhythmia the heart tissue which causes the arrhythmia is destroyed by heat, e.g. applying a laser beam or high frequency electrical energy, e.g. RF or microwave, to a desired location on the patient's endocardium
In the latter instance, the location of the tissue site causing or involved with the arrhythmia must be accurately known in order to be able to contact the desired location with a tissue destroying device. A major problem of ablating the site of the origin of the signals or a conductive pathway is to accurately determine the location of the site so that an excessive amount of good tissue is not damaged or destroyed along with the arrhythmogenic site, while at the same time ensuring that the arrhythmia does not return. For example, the average arrhythmogenic site consists of an area of about 1.4 cm.sup.2 of endocardial tissue, whereas a re-entrant site might be much larger. RF ablation techniques produce lesions about 0.5 cm.sup.2 in area, so several lesions may be necessary to completely ablate an area of interest. If the arrhythmogenic or re-entrant site is not accurately mapped, much good tissue surrounding the site will be unnecessarily damaged or destroyed.
A variety of prior methods have been used to detect electrical activity within a patient's heart to facilitate the mapping of electrical activity causing the arrhythmia. A number of these prior methods are disclosed in U.S. Patents which use elongated intravascular signal sensing devices with one or more electrodes on a distal portion of the device which are advanced through the patient's vasculature until the distal portions of the sensing devices are disposed within one or more of the patient's heart chambers with one or more electrodes in contact with the endocardial lining. While this procedure is widely used, it does not always allow the site of arrhythmogenic signals to be accurately determined.
In copending application Ser. No. 08/188,619, filed Jan. 27, 1994, now U.S. Pat. No. 5,509,411, reference is made to intravascular devices which are advanced through a patient's coronary arteries or cardiac veins to desired locations in the patient's epicardium where electrical activity is detected by means of electrodes on the distal ends of the devices to locate arrhythmogenic sites or conductive pathways causing or involved with arrhythmia. In copending application Ser. No. 08/207,918, filed Mar. 8, 1994, now abandoned, an intravascular device is described which uses RF energy to occlude a blood vessel in order to destroy tissue distal to the catheter by creating ischemic conditions therein.
What has been needed is a method and system for accurately detecting the source of signals which cause the arrhythmia and to create an lesion which effectively terminates the arrhythmia without detrimentally effecting tissue not involved with the arrhythmia.